Like others, I've been tweaking my putting stroke for as long as I've been playing. The upside of changing it up and trying new things has been that, overall, I putt equally well (or poorly!) with several different styles. On a day-to-day basis, one may be working better than the other. On a long-term basis, my overall putting is better now than ever and has improved gradually since I started. Like Monocacy says above, confidence and not overthinking are key.
Most days I'm confident anywhere inside the circle. On good days I'm confident out to 45-50 feet with either staggered or straddle, assuming no wind. (That doesn't mean I make even close to 50% of the long ones, just that I believe I can and I do it often enough to keep the confidence up.)
How long does it take? I don't know; I'm still working on it.
There's been a lot of short-term ups-and-downs but steady improvement over the long term.
I see an advantage to practicing and having confidence in more than one style of putting. My go-to is a staggered stance, mostly spin putt. If that is not working, if I miss a couple of easy ones, I will switch to a straddle style. If it's 'one of those days' and the straddle is not working either, I'll alternate hole-by-hole until I find the groove again. I went through a bad case of putting yips shortly after I started playing competitively and found that switching styles like that helped keep the overthinking and yips at bay.
I believe that practicing many styles - turbo putts, flick putts, upside-down putts, scoobers - will lead to overall improvement to which ever is your 'main style' on any given day.
Perfection in putting is a journey ... has *anyone* ever arrived at the destination??? Keep grinding. Enjoy the trip!